64 /* * Buffer slots: two mbuf clusters buffer the incoming packets. * The model has three slots. Sbuf is always occupied. * sbuf (store) - Receive interrupt puts packets here. * hbuf (hold) - When sbuf is full, put cluster here and * wakeup read (replace sbuf with fbuf). * fbuf (free) - When read is done, put cluster here. * On receiving, if sbuf is full and fbuf is 0, packet is dropped. */ /* store slot */